Soil Contamination- Overview and Case Study www.AssignmentPoint.com

How soil becomes Contaminated Urban runoff Agricultural runoff Mining Industrial Operations Atmospheric Deposition Contaminated Groundwater

Sources of Contamination

Gas Works Park

Gas Works Park Previous site of coal and oil gasification (1900 to 1956) Waste accmulations include: coal, tar, and oil Polynuclear aromatic hydrocarbons (PAH’s )and volatile organic compounds (VOC’s) are present in groundwater PCB’s, heavy metals, and cyanides also present “Gas Works deposit” is as thick as 9 feet across the park and overlies the Vashon Till- consists of waste products from prior operations ( Developed by Seattle Parks and Recreation and subsequently studies by USGS and UW

Borehole and Well Sites- Contour Map

Water Table Contour Map and Flow Paths

Geologic Cross Sections Important to understand the “Gas Works Deposit” as It’s interaction with the Ground Water is the main concern

Contamination processes Weathering of Hydrocarbons in soil and NAPL’s Weathering- dissoultion, volatilization, biodegradation These processes release water-soluble, low molecular weight orgainc compunds into water, leaving behind stained soils containing insoluble, high molecular weight compounds

Not Quite Polluted Enough… …to become a superfund site (in 1980) But polluted enough to cost tens of millions of dollars to clean up… Puget Sound Energy and City of Seattle still continuing to monitor and clean the site

Main Concerns/ Remediation Techniques Benzene (toxic/ Carcinogenic) Naphthalene (Toxic/ non-carcinogenic) PAHs (vary depending on type but can be both Toxic and Carcinogenic) Air sparging/ Soil Vapor Extraction (AS/SVE) Monitored Natural Attenuation (possible phyto-remediation to be used in future) Direct Soil contact Remedy

Air Sparging

Air Sparging/ Soil Vapor Extraction (AS/SVE)

Phytoremediation